1. Field of the Invention
The present invention relates to an electron emission source, a method of preparing the same, and an electron emission device employing the electron emission source, and more particularly, to an electron emission source having long lifespan without reducing current density, a method of preparing the same, and an electron emission device employing the electron emission source to have improved reliability.
2. Description of the Related Art
An electron emission device includes an anode and a cathode. A voltage is applied between the anode and the cathode to form an electric field. As a result, an electron emission source of the cathode emits electrons. The electrons collide with a phosphorous material of the anode to emit light.
A carbon-based material including a carbon nanotube (CNT), which has strong electron conductivity, has various advantages such as strong conductivity, high field enhancement effect, a low work function, and excellent electron emitting characteristics. Furthermore, the carbon-based material can be operated at low voltage, and manufactured in a large area. Therefore, the carbon-based material is expected to be an ideal electron emission source of an electron emitting device.
Methods of preparing electron emission sources containing carbon nanotubes include, for example, a carbon nanotube growing method using chemical vapor deposition (CVD), etc., a paste method using a composition for forming electron emission sources that contain carbon nanotubes. When using the paste method, the manufacturing costs decrease, and large-area electron emission sources can be obtained.
Examples of the composition for forming electron emission sources that contains carbon nanotubes are disclosed, for example, in U.S. Pat. No. 6,436,221.
In electron emission sources containing carbon nanotubes, the temperature of the end of carbon nanotubes is increased to 1,500 K or higher by joule heating when emitting electrons. Due to this, the carbon nanotubes react with oxygen in electron emission devices during driving the devices, resulting in deterioration of electron emission sources. This adversely affects the lifespan of electron emission devices.